Children with Severe Allergies Susceptible to Rebound Reactions

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It's fairly common for children who have a severe allergic
reaction known as anaphylaxis to be in danger of having a second,
delayed allergic reaction within hours of the first one, a new
study suggests.

Researchers in Canada found that about 15 percent of children who
came to the emergency room for anaphylaxis had a second
serious allergic reaction hours after the initial reaction.

The study also found that about 75 percent of these second
anaphylactic reactions, known as biphasic reactions, occurred
within 6 hours of their first anaphylaxis symptoms, and in most
cases, the children were still at the ER because of their first
reaction. The children's symptoms included difficulty breathing,
low blood pressure, hives or swelling, nausea and dizziness.

"The study found that delayed reactions were more likely to
happen if the initial allergic reaction in children was severe,
and if it was not treated with epinephrine," said Dr. Waleed
Alqurashi, the study's lead author and an emergency physician at
Children's Hospital of Eastern Ontario in Ottawa, Canada.
[ 8
Strange Signs You're Having an Allergic Reaction ]

These delayed reactions tend to occur when the initial symptoms
of an allergic reaction go away, but then return hours or even
days later — without additional exposure to the substance
that caused the allergic reaction, he said.

One possible reason children may develop these delayed allergic
reactions is that they seem to experience an inflammatory
response that lasts longer than it does in adults, Alqurashi
said.

In children, common triggers of these serious allergic reactions
might include insect stings, medications, and foods like nuts,
seafood, milk and eggs, he said.

An anaphylactic reaction is a medical emergency requiring
immediate treatment with a shot of the hormone epinephrine
(adrenaline). Many kids who are at risk of having these serious
allergic reactions are advised to carry an
EpiPen, a prescription medication that can be
self-administered or given by a parent or school nurse, to
control symptoms that can come on rapidly and worsen quickly and,
in some cases, be fatal.

Delayed treatment

The occurrence of anaphylactic reactions in children seems to be
on the rise, according to the researchers. But there's limited
information about how frequently children go on to have a second
severe allergic reaction, or about which children might be more
vulnerable to having them.

In the study, published online June 22 in the journal Annals of
Allergy, Asthma and Immunology, the researchers analyzed the
medical records of about 500 children who were treated at the
emergency rooms of two large Canadian children's hospitals over a
one-year period.

The findings suggested that children who may be at increased risk
for delayed allergic reactions are those who were given
medications for asthma at the hospital, had signs of anaphylactic
shock when they arrived at the emergency room and needed multiple
treatments with epinephrine for their initial anaphylactic
reaction, Alqurashi said.

In addition, the results showed that anaphylaxis tended to be
more severe in children when epinephrine administration was
delayed.

"Epinephrine is the single most
important treatment for anaphylaxis," Alqurashi said. He
explained that, when the drug is given promptly after the start
of an allergic reaction, it controls and limits the immune
system's response to a known allergy trigger.

"The key message for parents, caregivers and first responders is
to administer epinephrine at the first sign of a severe allergic
reaction to prevent anaphylaxis from worsening," Alqurashi said.